Rheumatoid arthritis--the clinical significance of histo- and immunopathological abnormalities in normal skin.

Biopsies of normal skin from 64 patients with rheumatoid arthritis (RA) were studied for histological abnormalities in dermal blood vessels. Thirty percent of patients had a moderate or dense infiltrate of mononuclear cells (predominantly T lymphocytes) around the vessel walls not seen in controls. This infiltrate correlated with disease activity and the presence of extraarticular manifestations. Vascular deposits of IgM often with C3 were seen in seropositive patients only and correlated with the amount of cellular infiltrate. No Ig and C deposits were seen in biopsies of seronegative patients and healthy controls. Apart from IgM and C3, IgG and/or IgA were found perivascularly in the areas of skin with leukocytoclastic vasculitis, indicating participation of other classes of immunoglobulins in immune complexes. The histological and/or immunopathological features that we found in uninvolved skin may serve as markers of disease activity and extraarticular manifestations.